Light guide illumination device with light divergence modifier

ABSTRACT

An illumination device includes a light-emitting element (LEEs); a light guide extending in a forward direction from a first end to a second end to receive at the first end LEE light and to guide the light to the second end, such that divergence of the light received at the first end and divergence of the guided light that reaches the second end are substantially the same; a light divergence modifier optically coupled to the light guide at the second end to receive the guided light, to modify the divergence of the guided light, such that the light provided by the light divergence modifier has a modified divergence different from the divergence of the guided light; and an optical extractor optically coupled to the light divergence modifier, to output into the ambient environment light provided by the light divergence modifier as output light in one or more output angular ranges.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No.14/418,887, filed Jan. 30, 2015, which is a U.S. National Stage ofInternational Application No. PCT/US2014/056132, filed Sep. 17, 2014,which claims benefit under 35 U.S.C. § 119(e)(1) of U.S. ProvisionalApplication No. 61/878,764, filed on Sep. 17, 2013, the entire contentsof which are incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to illumination devices having acombination of a light guide and a light divergence modifier.

BACKGROUND

Light sources are used in a variety of applications, such as providinggeneral illumination and providing light for electronic displays (e.g.,LCDs). Historically, incandescent light sources have been widely usedfor general illumination purposes. Incandescent light sources producelight by heating a filament wire to a high temperature until it glows.The hot filament is protected from oxidation in the air with a glassenclosure that is filled with inert gas or evacuated. Incandescent lightsources are gradually being replaced in many applications by other typesof electric lights, such as fluorescent lamps, compact fluorescent lamps(CFL), cold cathode fluorescent lamps (CCFL), high-intensity dischargelamps, and solid state light sources, such as light-emitting diodes(LEDs).

SUMMARY

The present disclosure relates to illumination devices that include acombination of a light guide and a light divergence modifier.

In general, innovative aspects of the technologies described herein canbe implemented in an illumination device that includes one or more ofthe following aspects:

In one aspect, an illumination device includes a plurality oflight-emitting elements (LEEs); a light guide extending in a forwarddirection from a first end of the light guide to a second end of thelight guide, the light guide being positioned to receive at the firstend light emitted by the LEEs and configured to guide the light to thesecond end, wherein divergence of the light received at the first endand divergence of the guided light that reaches the second end aresubstantially the same; a light divergence modifier optically coupled tothe light guide at the second end to receive the guided light, the lightdivergence modifier configured to modify the divergence of the guidedlight, such that the light provided by the light divergence modifier hasa modified divergence different from the divergence of the guided light;and an optical extractor optically coupled to the light divergencemodifier, the optical extractor configured to output into the ambientenvironment light provided by the light divergence modifier as outputlight in one or more output angular ranges.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. In someimplementations, the light divergence modifier can be tapered such thatan input aperture of the light divergence modifier is larger than anoutput aperture of the light divergence modifier, and the modifieddivergence of the light provided—at the output aperture of the lightdivergence modifier—to the optical extractor is larger than thedivergence of the guided light. In other implementations, the lightdivergence modifier can be flared such that an input aperture of thelight divergence modifier is smaller than an output aperture of thelight divergence modifier, and the modified divergence of the lightprovided—at the output aperture of the light divergence modifier—to theoptical extractor is smaller than the divergence of the guided light. Ineither of the foregoing implementations, the light divergence modifiercan include a pair of opposing side surfaces extending along a length ofthe light divergence modifier between the input aperture and the outputaperture. In some cases, at least one of the opposing side surfaces isplanar. In some other cases, both of the opposing side surfaces areplanar. Alternatively, the light divergence modifier can include atruncated conical shaped surface extending between the input apertureand the output aperture.

In some implementations, the light divergence modifier is configured toguide the light received at the input aperture in the forward directionthrough total internal reflection (TIR) at the opposing side surfaces.

In some implementations, the light divergence modifier can include a 3Dgrating extending along a length of the light divergence modifier, the3D grating configured such that the modified divergence of the lightprovided—at the output aperture of the light divergence modifier—to theoptical extractor is smaller than the divergence of the guided light. Insome implementations, the light divergence modifier can include a 3Dgrating extending along a length of the light divergence modifier, the3D grating configured such that the modified divergence of the lightprovided—at the output aperture of the light divergence modifier—to theoptical extractor is larger than the divergence of the guided light.

In either of the foregoing implementations, the length of the lightdivergence modifier is a fraction of a length of the light guide. Forexample, the fraction is between 5% and 50%. Further, the 3D grating caninclude one or more of a holographic element and a photonic crystal.

In some implementations, the light divergence modifier comprises aconvergent lens configured such that the modified divergence of thelight provided to the optical extractor is smaller than the divergenceof the guided light. In other implementations, the light divergencemodifier comprises a divergent lens configured such that the modifieddivergence of the light provided to the optical extractor is larger thanthe divergence of the guided light. Here, an index of refractionassociated with the lens is different from an index of refractionassociated with the light guide and an index of refraction associatedwith the optical extractor. In some cases, the lens can be a Fresnellens.

In either of the foregoing implementations, the light guide, the lightdivergence modifier and the optical extractor can be integrally formedor bonded together.

In some implementations, the light divergence modifier can include anoptical interface configured as a 2D grating, the 2D grating configuredsuch that the modified divergence of the light provided to the opticalextractor is smaller than the divergence of the guided light. In someimplementations, the light divergence modifier can include an opticalinterface configured as a 2D grating, the 2D grating configured suchthat the modified divergence of the light provided to the opticalextractor is larger than the divergence of the guided light.

In some implementations, the light guide can be configured to guide thelight received at the first end in the forward direction through totalinternal reflection (TIR) off the opposing side surfaces. In someimplementations, the light provided by the LEEs has a first divergence,and a numerical aperture of the light guide is such that the lightreceived from the LEEs with the first divergence can be guided by thelight guide through TIR off the pair of opposing side surfaces.

In some implementations, the disclosed luminaire module can furtherinclude one or more optical couplers. Here, the light provided by theLEEs has a first divergence, the optical couplers are arranged toreceive the light provided by the LEEs and redirect it to the receivingend of the light guide with a second divergence, and a numericalaperture of the light guide is such that the light received from theoptical couplers with the second divergence can be guided by the lightguide through TIR off the pair of opposing side surfaces.

In some implementations, the LEEs can be LEDs that emit white light. Insome implementations, the optical extractor can include at least oneredirecting surface, the at least one redirecting surface of the opticalextractor being adapted to reflect at least a portion of the lightprovided by the light divergence modifier in a direction that has acomponent orthogonal to the forward direction. In some implementations,the optical extractor can include a first redirecting surface adapted toreflect at least a portion of the light provided by the light divergencemodifier in a first direction that has a component orthogonal to theforward direction; and a second redirecting surface adapted to reflectat least a portion of the light provided by the light divergencemodifier in a second direction that has a component orthogonal to theforward direction and antiparallel to the orthogonal component of thefirst direction. In either of the foregoing implementations, the firstredirecting surface and/or the second redirecting surface can transmit aremaining portion of the light provided by the light divergence modifierso that the transmitted portion of the light exits the optical extractorto the ambient environment in the forward direction. Moreover, theoptical extractor can include a first curved output surface and/or asecond curved output surface positioned in a path(s) of the lightreflected from the first redirecting surface and/or the secondredirecting surface, and the first curved output surface and/or thesecond curved output surface are configured to transmit light incidentthereon to the ambient environment in one or more backward angularranges.

In some implementations, the disclosed luminaire module can extendorthogonally to the forward direction. Here, the LEEs are arrangedorthogonally to the forward direction.

The details of one or more implementations of the technologies describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features, aspects, and advantages of the disclosedtechnologies will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an example of a luminaire module that includes acombination of a light guide and a light divergence modifier.

FIG. 1B is an example intensity profile of the luminaire module shown inFIG. 1A.

FIGS. 2A-2F show aspects of example luminaire modules that include acombination of a light guide and a light divergence modifier.

FIGS. 3A-3G show examples of luminaire modules that include differentcombinations of a light guide with different light divergence modifiers.

Reference numbers and designations in the various drawings indicateexemplary aspects, implementations of particular features of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure relates to illumination devices for providingdirect and/or indirect illumination. The disclosed illumination devicescan efficiently guide and distribute light emitted by solid-state lightsources towards work surfaces and/or towards background regions. Variousluminous surfaces of the disclosed illumination devices and theirrespective intensity vectors can be manipulated within an illuminatedenvironment to provide good utility of the light distribution output bythe disclosed illumination devices. The present technology can harnessthe collective output of a plurality of solid-state light sources andcreate a virtual light source with unique properties that can result incompact luminaires with a small physical footprint relative to theilluminated environment.

Here, the light from the solid-state light sources is received at aninput end of a light guide and guided to an output end. The guided lightat the output end of the light guide can have the same or different(within measurement error) divergence compared to the light received atthe input end of the light guide. An optical element, referred to hereinas a light divergence modifier, is disposed between the light guide andan optical extractor of the disclosed illumination devices. In thismanner, the light divergence modifier receives the guided light andmodifies the divergence of the guided light such that light provided bythe light divergence modifier to the optical extractor has a modifieddivergence that is different from the divergence of the guided light.

(i) Illumination Device with a Combination of a Light Guide and a LightDivergence Modifier

FIG. 1A illustrates a block diagram of an illumination device 100 thatincludes a combination of a light guide 130 and a light divergencemodifier 150. The illumination device 100, referred to as luminairemodule 100, further includes one or more light emitting elements (LEEs)110, an optical extractor 140. The LEEs 110 can be disposed on asubstrate 105. In some implementations, the illumination device 100further includes one or more couplers 120.

In general, a LEE, also referred to as a light emitter, is a device thatemits radiation in one or more regions of the electromagnetic spectrumfrom among the visible region, the infrared region and/or theultraviolet region, when activated. Activation of a LEE can be achievedby applying a potential difference across components of the LEE orpassing a current through components of the LEE, for example. A LEE canhave monochromatic, quasi-monochromatic, polychromatic or broadbandspectral emission characteristics. Examples of LEEs includesemiconductor, organic, polymer/polymeric light-emitting diodes, othermonochromatic, quasi-monochromatic or other light-emitting elements. Insome implementations, a LEE is a specific device that emits theradiation, for example a LED die. In other implementations, the LEEincludes a combination of the specific device that emits the radiation(e.g., a LED die) together with a housing or package within which thespecific device or devices are placed. Examples of LEEs include alsolasers and more specifically semiconductor lasers, such as verticalcavity surface emitting lasers (VCSELs) and edge emitting lasers.Further examples of LEEs include superluminescent diodes and othersuperluminescent devices.

During operation, the LEEs 110 provide light within a first angularrange 115. Such light can have a Lambertian distribution relative to theoptical axes of the one or more LEEs 110 (e.g., the z-axis of theCartesian reference system shown in FIG. 1A.) As used herein, providinglight in an “angular range” refers to providing light that propagates inone or more directions having a divergence with respect to acorresponding prevalent direction of propagation. In this context, theterm “prevalent direction of propagation” refers to a direction alongwhich all or a portion of an intensity distribution of the propagatinglight has a maximum, a mean, a median or other defined direction, forexample. For example, the prevalent direction of propagation associatedwith the angular range can be an orientation of a lobe of the intensitydistribution. (See, e.g., FIG. 1B.) Also in this context, the term“divergence” refers to a solid angle outside of which the intensitydistribution of the propagating light drops below a predefined fractionof the intensity in the prevalent direction of the intensitydistribution. For example, the divergence associated with the angularrange can be the width of the lobe of the intensity distribution. Thepredefined fraction can be 10%, 5%, 1%, or other portion of the maximumintensity, depending on the lighting application.

The light guide 130 can be made from a solid, transparent material. Thelight guide 130 is arranged to receive the light provided by the LEEs110 at one end of the light guide 130 and to guide the received light ina forward direction, e.g., along the z-axis, from the receiving end toan opposing end of the light guide 130. Here, a distance D between thereceiving end of the light guide 130 and its opposing end can be 5, 10,20, 50 or 100 cm, for instance. A combination of (i) an angular range inwhich the light is received by the light guide 130 at the receiving endand (ii) a numerical aperture of the light guide 130 is configured suchthat the received light is guided from the receiving end to the opposingend through reflection off of light guide side surfaces 132 a, 132 b ofthe light guide 130. Depending on the implementation, at least some, ifnot all, of this reflection is via total internal reflection (TIR). Insome implementations, the numerical aperture of the light guide 130 issuch that all light provided by the LEEs 110 in the angular range 115can be injected directly into the light guide 130 at its receiving end.

In other implementations, the luminaire module 100 includes one or morecouplers 120 to receive the light from the LEEs 110 within the firstangular range 115 and provide light within a second angular range 125 tothe receiving end of the light guide 130. The one or more couplers 120are shaped to transform the first angular range 115 into the secondangular range 125 via total internal reflection, specular reflection orboth. As such, the one or more couplers 120 can include a solidtransparent material for propagating light from an input end to anoutput end of each of the one or more couplers 120. Here, the divergenceof the second angular range 125 is smaller than the divergence of thefirst angular range 115, such that all light provided by the couplers120 in the angular range 125 can be injected into the light guide 130 atits receiving end.

One or more of the light guide side surfaces 132 a, 132 b can be planar,curved or otherwise shaped. The light guide side surfaces 132 a, 132 bcan be parallel or non-parallel. In embodiments with non-parallel lightguide side surfaces 132 a, 132 b, a third angular range 135 of theguided light at the opposing end of the light guide 130 is differentthan the angular range 115 (when the light guide 130 receives the lightdirectly from the LEEs 110) or 125 (when the light guide 130 receivesthe light from the couplers 120) of the light received at the receivingend. Here, the light guide side surfaces 132 a, 132 b can be opticallysmooth to allow for the guided light to propagate forward (e.g., in thepositive direction of the z-axis) inside the light guide 130 throughTIR. In this case, the light guide side surfaces 132 a, 132 b are shapedand arranged with respect to the z-axis and each other such that theguided light impinges on the light guide side surfaces 132 a, 132 b atincident angles larger than a critical angle over the entire distanceD—from the input end the output end of the light guide 130. Inembodiments with parallel light guide side surfaces 132 a, 132 b,whether the light guide 130 is solid or hollow, the third angular range135 of the guided light at the opposing end of the light guide 130 hasat least substantially the same divergence as the angular range 115(when the light guide 130 receives the light directly from the LEEs 110)or 125 (when the light guide 130 receives the light directly from thecouplers 120) of the light received at the receiving end.

Additionally, the length D of the light guide 130 (along the z-axis), awidth L (along the y-axis) and a thickness T (along the x-axis) aredesigned to homogenize the light emitted by the discrete LEEs 110—whichare distributed along the y-axis—as it is guided from the receiving endto the opposing end of the light guide 130. In this manner, thehomogenizing of the emitted light—as it is guided through the lightguide 130—causes a change of a discrete profile along the y-axis of thefirst angular range 115 (when the light guide 130 receives the lightdirectly from the LEEs 110) or the second angular range 125 (when thelight guide 130 receives the light from the couplers 120) to acontinuous profile along the y-axis of the third angular range 135 inwhich the discrete profile is partially or fully blurred.

The light divergence modifier 150 is disposed between the output end ofthe light guide 130 and the optical extractor 140. In someimplementations, the light divergence modifier 150 extends from an inputaperture to an output aperture over a distance Δ. The distance Δrepresents a length of the light divergence modifier 150 and it isfinite (Δ>0) but less than the depth D of the light guide 130, asdescribed below in connection with FIGS. 3A-3E and 3F.

In some implementations, the length Δ of the light divergence modifier150 is between 0.05 D≤Δ≤0.5 D, e.g., 0.1 D, 0.2 D, 0.3 D, or 0.4 D. Insome cases, the light divergence modifier 150 is made from a solid,transparent material. For example, the light divergence modifiermaterial has the same refractive index as the light guide material or asthe optical extractor material. As another example, the light divergencemodifier material has a refractive index different from at least one ofrefractive indices of the light guide material and the optical extractormaterial. In the latter example, either the light guide 130 or theoptical extractor 140 or both also is/are hollow. In other cases, thefinite-length light divergence modifier 150 is hollow. In such cases,either the light guide 130 or the optical extractor 140 or both alsois/are hollow.

In other implementations, the light divergence modifier 150 isconfigured as an interfacial light divergence modifier which includes anoptical interface between the light guide 130 and the optical extractor140. Here, the foregoing optical interface is engineered (as describedbelow in connection with FIG. 3G) to modify the angular range 135 of theguided light. In the latter case, the length Δ of the light divergencemodifier 150 collapses to zero, Δ→0.

The guided light provided at the output end of the light guide 130 witha guided angular range 135 is received by the light divergence modifier150 at the input aperture. The light divergence modifier 150 isconfigured to modify the angular range 135 of the received guided lightsuch that light provided by the light divergence modifier 150 at theoutput aperture has a modified angular range 155. In this manner, adivergence of the modified angular range 155 is different from adivergence of the guided angular range 135, or equivalently, thedivergence of the modified light provided by the light divergencemodifier 150 to the optical extractor 140 is different from thedivergence of the guided light received by the light divergence modifier150 from the light guide 130.

The optical extractor 140 outputs into the ambient environment the lightwith modified angular range 155 received from the light divergencemodifier 150 as output light in one or more output angular ranges. Assuch, the light output by the extractor 140 has a first output angularrange 145′ that can be substantially continuous along the y-axis and hasa first output propagation direction with a component opposite to theforward direction (e.g., antiparallel to the z-axis.) In someimplementations, the light output by the extractor 140 has, in additionto the first output angular range 145′, a second output angular range145″ that is substantially continuous along the y-axis and has a secondoutput propagation direction with a component opposite to the forwarddirection (e.g., antiparallel to the z-axis.) In this case, the firstoutput propagation direction and the second output propagation directionhave respective components orthogonal to the forward direction that areopposite (antiparallel) to each other (e.g., antiparallel and parallelto the x-axis.) In some implementations, the light output by theextractor 140 has, in addition to the first output angular range 145′and the second output angular range 145″, a third output angular range145′″ that can be substantially continuous along the y-axis and has athird output propagation direction along the forward direction (e.g.,along the z-axis.)

As described above, the light guide 130 and the optical extractor 140 ofillumination device 100 are arranged and configured to translate andredirect light emitted by LEEs 110 away from the LEEs before the lightis output into the ambient environment. The spatial separation of theplace of generation of the light, also referred to as the physical(light) source, from the place of extraction of the light, also referredto as a virtual light source or a virtual filament, can facilitatedesign of the illumination device 100. In this manner, a virtualfilament can be configured to provide substantially non-isotropic lightemission with respect to planes parallel to an optical axis of theillumination device (for example the z-axis.) In contrast, a typicalincandescent filament generally emits substantially isotropicallydistributed amounts of light. The virtual filament(s) may be viewed asone or more portions of space from which substantial amounts of lightappear to emanate. Furthermore, separating the LEEs 110, with theirpredetermined optical, thermal, electrical and mechanical constraints,from the place of light extraction, may facilitate a greater degree ofdesign freedom of the illumination device 100 and allows for an extendedoptical path, which can permit a predetermined level of light mixingbefore light is output from the illumination device 100.

Moreover, the use of a light divergence modifier 150 in the illuminationdevice 100 to modify divergence of the light guided by the light guide130 prior to providing it to the optical extractor 140 is advantageousfor cases when near field and far filed intensity properties of thelight output by the illumination device 100 need to be furthercustomized. For example, a light divergence modifier 150 having anoutput aperture narrower than an input aperture (as described below inconnection with FIG. 3A, for instance) can be used to expand divergenceof the modified angular range 155 relative to divergence of the guidedangular range 135. The wider divergence of the modified light providedby the light divergence modifier 150 to the extractor surface can beexploited to increase the divergence of the light output by the opticalextractor 140 into the ambient environment for lowered luminousintensity and perhaps more uniform spatial near field luminance.Oppositely, a light divergence modifier 150 having an output aperturewider than an input aperture can be used (as described below inconnection with FIG. 3B, for instance.) The latter embodiment could thusprovide a higher output luminous intensity in a given peak directionbecause of the narrower divergence of the modified angular range 155relative to divergence of the guided angular range 135. As anotherexample, a light divergence modifier 150 that is asymmetric relative tothe y-z plane can be used to change the prevalent propagation directionof the modified angular range 155 relative the prevalent propagationdirection of the guided angular range 135. Each of these variations isdirected to the ability to manipulate the zonal luminous intensityprofile and near field luminance properties of the exit surfaces of theextractor 140.

FIG. 1B shows an x-z cross-section of an example far-field lightintensity profile 101 of the illumination device 100 that is elongatedalong the y-axis (perpendicular to the sectional plane of FIG. 1A). Insome implementations, the far-field light intensity profile 101 includesa first output lobe 145 a representing light output by the illuminationdevice 100 in the first output angular range 145′. In this case, apropagation direction of the first output angular range 145′ is alongthe about −130° bisector of the first output lobe 145 a. In someimplementations, in addition to the first output lobe 145 a, thefar-field light intensity profile 101 includes one or more of a secondoutput lobe 145 b representing light output by the illumination device100 in the second output angular range 145″ or a third output lobe 145 crepresenting light output by the illumination device 100 in the thirdoutput angular range 145′″. In this case, a propagation direction of thesecond output angular range 145″ is along the about +130° bisector ofthe second output lobe 145 b and a propagation direction of the thirdoutput angular range 145′″ is along the about 0° bisector of the thirdoutput lobe 145 c.

In this case, each of a divergence of the first output angular range145′ (represented by a width of the first output lobe 145 a) and adivergence of the second output angular range 145″ (represented by awidth of the second output lobe 145 b) is smaller than a divergence ofthe third output angular range 145′″ (represented by a width of thethird output lobe 145 c). In general, composition and geometry of thecouplers 120, the light guide 130, the light divergence modifier 150 andthe extractor 140 of the illumination device 100 can affect thefar-field light intensity profile 101, e.g., the propagation directionand divergence associated with the first output lobe 145 a, and,optionally, of the second 145 b and third 145 c output lobes. Asdescribed in detail below, divergencies of the output angular ranges145′, 145″ and 145′″ (represented by respective widths of the firstoutput lobe 145 a, the second output lobe 145 b and the third outputlobe 145 c) can specifically depend on a configuration of the lightdivergence modifier 150. Additionally, the configuration of the lightdivergence modifier 150 can also influence the prevalent propagationdirection of at least the third output angular range 145′″ (representedby an orientation of the third output lobe 145 c).

Prior to describing details of various embodiments of the illuminationdevice 100 that are configured with a combination of a light guide and alight divergence modifier, a light guide illumination device isdescribed for which the light guide provides the guided light directlyto the optical extractor, without the use of a light divergencemodifier.

(ii) Light Guide Luminaire Module without a Light Divergence Modifier

Referring to FIG. 2A, in which a Cartesian coordinate system is shownfor reference, a luminaire module 200 includes a mount 212 having aplurality of LEEs 210 distributed along a first surface of the mount212. The mount with the LEEs 210 is disposed at a first (e.g., upper)edge 231 of a light guide 230. Once again, the positive z-direction isreferred to as the “forward” direction and the negative z-direction isthe “backward” direction. Sections through the luminaire module 200parallel to the x-z plane are referred to as the “cross-section” or“cross-sectional plane” of the luminaire module. Also, luminaire module200 extends along the y-direction, so this direction is referred to asthe “longitudinal” direction of the luminaire module. Implementations ofluminaire modules can have a plane of symmetry parallel to the y-zplane, be curved or otherwise shaped. This is referred to as the“symmetry plane” of the luminaire module.

Multiple LEEs 210 are disposed on the first surface of the mount 212,although only one of the multiple LEEs 210 is shown in FIG. 2A. Forexample, the plurality of LEEs 210 can include multiple white LEDs. TheLEEs 210 are optically coupled with one or more optical couplers 220(only one of which is shown in FIG. 2A). An optical extractor 240 isdisposed at second (e.g., lower) edge 232 of light guide 230.

Mount 212, light guide 230, and optical extractor 240 extend a length Lalong the y-direction, so that the luminaire module is an elongatedluminaire module with an elongation of L that may be about parallel to awall of a room (e.g., a ceiling of the room). Generally, L can vary asdesired. Typically, L is in a range from about 1 cm to about 200 cm(e.g., 20 cm or more, 30 cm or more, 40 cm or more, 50 cm or more, 60 cmor more, 70 cm or more, 80 cm or more, 100 cm or more, 125 cm or more,or, 150 cm or more).

The number of LEEs 210 on the mount 212 will generally depend, interalia, on the length L, where more LEEs are used for longer luminairemodules. In some implementations, the plurality of LEEs 210 can includebetween 10 and 1,000 LEEs (e.g., about 50 LEEs, about 100 LEEs, about200 LEEs, about 500 LEEs). Generally, the density of LEEs (e.g., numberof LEEs per unit length) will also depend on the nominal power of theLEEs and illuminance desired from the luminaire module. For example, arelatively high density of LEEs can be used in applications where highilluminance is desired or where low power LEEs are used. In someimplementations, the luminaire module 200 has LEE density along itslength of 0.1 LEE per centimeter or more (e.g., 0.2 per centimeter ormore, 0.5 per centimeter or more, 1 per centimeter or more, 2 percentimeter or more). The density of LEEs may also be based on a desiredamount of mixing of light emitted by the multiple LEEs. Inimplementations, LEEs can be evenly spaced along the length, L, of theluminaire module. In some implementations, a heat-sink 205 can beattached to the mount 212 to extract heat emitted by the plurality ofLEEs 210. The heat-sink 205 can be disposed on a surface of the mount212 opposing the side of the mount 212 on which the LEEs 210 aredisposed. The luminaire module 200 can include one or multiple types ofLEEs, for example one or more subsets of LEEs in which each subset canhave different color or color temperature.

Optical coupler 220 includes one or more solid pieces of transparentoptical material (e.g., a glass material or a transparent plastic, suchas polycarbonate or acrylic) having surfaces 221 and 222 positioned toreflect light from the LEEs 210 towards the light guide 230. In general,surfaces 221 and 222 are shaped to collect and at least partiallycollimate light emitted from the LEEs. In the x-z cross-sectional plane,surfaces 221 and 222 can be straight or curved. Examples of curvedsurfaces include surfaces having a constant radius of curvature,parabolic or hyperbolic shapes. In some implementations, surfaces 221and 222 are coated with a highly reflective material (e.g., a reflectivemetal, such as aluminum or silver), to provide a highly reflectiveoptical interface. The cross-sectional profile of optical coupler 220can be uniform along the length L of luminaire module 200.Alternatively, the cross-sectional profile can vary. For example,surfaces 221 and/or 222 can be curved out of the x-z plane.

The exit aperture of the optical coupler 220 adjacent upper edge oflight guide 231 is optically coupled to edge 231 to facilitate efficientcoupling of light from the optical coupler 220 into light guide 230. Forexample, the surfaces of a solid coupler and a solid light guide can beattached using a material that substantially matches the refractiveindex of the material forming the optical coupler 220 or light guide 230or both (e.g., refractive indices across the interface are different by2% or less.) The optical coupler 220 can be affixed to light guide 230using an index matching fluid, grease, or adhesive. In someimplementations, optical coupler 220 is fused to light guide 230 or theyare integrally formed from a single piece of material (e.g., coupler andlight guide may be monolithic and may be made of a solid transparentoptical material).

Light guide 230 is formed from a piece of transparent material (e.g.,glass material such as BK7, fused silica or quartz glass, or atransparent plastic, such as polycarbonate or acrylic) that can be thesame or different from the material forming optical couplers 220. Lightguide 230 extends length L in the y-direction, has a uniform thickness Tin the x-direction, and a uniform depth D in the z-direction. Thedimensions D and T are generally selected based on the desired opticalproperties of the light guide (e.g., which spatial modes are supported)and/or the direct/indirect intensity distribution. During operation,light coupled into the light guide 230 from optical coupler 220 (with anangular range 225) reflects off the planar surfaces of the light guideby TIR and spatially mixes within the light guide. The mixing can helpachieve illuminance and/or color uniformity, along the y-axis, at thedistal portion of the light guide 232 at optical extractor 240. Thedepth, D, of light guide 230 can be selected to achieve adequateuniformity at the exit aperture (i.e., at end 232) of the light guide.In some implementations, D is in a range from about 1 cm to about 20 cm(e.g., 2 cm or more, 4 cm or more, 6 cm or more, 8 cm or more, 10 cm ormore, 12 cm or more).

In general, optical couplers 220 are designed to restrict the angularrange of light entering the light guide 230 (e.g., to within +/−40degrees) so that at least a substantial amount of the light (e.g., 95%or more of the light) is optically coupled into spatial modes in thelight guide 230 that undergoes TIR at the planar surfaces. Light guide230 can have a uniform thickness T, which is the distance separating twoplanar opposing surfaces of the light guide. Generally, T issufficiently large so the light guide has an aperture at first (e.g.,upper) surface 231 sufficiently large to approximately match (or exceed)the exit aperture of optical coupler 220. In some implementations, T isin a range from about 0.05 cm to about 2 cm (e.g., about 0.1 cm or more,about 0.2 cm or more, about 0.5 cm or more, about 0.8 cm or more, about1 cm or more, about 1.5 cm or more). Depending on the implementation,the narrower the light guide the better it may spatially mix light. Anarrow light guide also provides a narrow exit aperture. As such lightemitted from the light guide can be considered to resemble the lightemitted from a one-dimensional linear light source, also referred to asan elongate virtual filament.

While optical coupler 220 and light guide 230 are formed from solidpieces of transparent optical material, hollow structures are alsopossible. For example, the optical coupler 220 or the light guide 230 orboth may be hollow with reflective inner surfaces rather than beingsolid. As such material cost can be reduced and absorption in the lightguide can be mitigated. A number of specular reflective materials may besuitable for this purpose including materials such as 3M Vikuiti™ orMiro IV™ sheet from Alanod Corporation where greater than 90% of theincident light can be efficiently guided to the optical extractor.

Optical extractor 240 is also composed of a solid piece of transparentoptical material (e.g., a glass material or a transparent plastic, suchas polycarbonate or acrylic) that can be the same as or different fromthe material forming light guide 230. In the example implementationshown in FIG. 2A, the optical extractor 240 includes redirecting (e.g.,flat) surfaces 242 and 244 and curved surfaces 246 and 248. The flatsurfaces 242 and 244 represent first and second portions of aredirecting surface 243, while the curved surfaces 246 and 248 representfirst and second output surfaces of the luminaire module 200.

Surfaces 242 and 244 are coated with a reflective material (e.g., ahighly reflective metal such as aluminum or silver) over which aprotective coating may be disposed. For example, the material formingsuch a coating may reflect about 95% or more of light incident thereonat appropriate (e.g., visible) wavelengths. Here, surfaces 242 and 244provide a highly reflective optical interface for light having theangular range 225 entering an input end of the optical extractor 232′from light guide 230. As another example, the surfaces 242 and 244include portions that are transparent to the light entering at the inputend 232′ of the optical extractor 240. Here, these portions can beuncoated regions (e.g., partially silvered regions) or discontinuities(e.g., slots, slits, apertures) of the surfaces 242 and 244. As such,some light is transmitted in the forward direction (along the z-axis)through surfaces 242 and 244 of the optical extractor 240 in an outputangular range 225′. In some cases, the light transmitted in the outputangular range is refracted. In this way, the redirecting surface 243acts as a beam splitter rather than a mirror, and transmits in theoutput angular range 225′ a desired portion of incident light, whilereflecting the remaining light in angular ranges 138 and 138′.

In the x-z cross-sectional plane, the lines corresponding to surfaces242 and 244 have the same length and form an apex or vertex 241, e.g. av-shape that meets at the apex 241. In general, an included angle (e.g.,the smallest included angle between the surfaces 244 and 242) of theredirecting surfaces 242, 244 can vary as desired. For example, in someimplementations, the included angle can be relatively small (e.g., from30° to 60°). In certain implementations, the included angle is in arange from 60° to 120° (e.g., about 90°). The included angle can also berelatively large (e.g., in a range from 120° to 150° or more). In theexample implementation shown in FIG. 2A, the output surfaces 246, 248 ofthe optical extractor 240 are curved with a constant radius of curvaturethat is the same for both. In an aspect, the output surfaces 246, 248may have optical power (e.g., may focus or defocus light.) Accordingly,luminaire module 200 has a plane of symmetry intersecting apex 241parallel to the y-z plane.

The surface of optical extractor 240 adjacent to the lower edge 232 oflight guide 230 is optically coupled to edge 232. For example, opticalextractor 240 can be affixed to light guide 230 using an index matchingfluid, grease, or adhesive. In some implementations, optical extractor240 is fused to light guide 230 or they are integrally formed from asingle piece of material.

The emission spectrum of the luminaire module 200 corresponds to theemission spectrum of the LEEs 210. However, in some implementations, awavelength-conversion material may be positioned in the luminairemodule, for example remote from the LEEs, so that the wavelengthspectrum of the luminaire module is dependent both on the emissionspectrum of the LEEs and the composition of the wavelength-conversionmaterial. In general, a wavelength-conversion material can be placed ina variety of different locations in luminaire module 200. For example, awavelength-conversion material may be disposed proximate the LEEs 210,adjacent surfaces 242 and 244 of optical extractor 240, on the exitsurfaces 246 and 248 of optical extractor 240, and/or at otherlocations.

The layer of wavelength-conversion material (e.g., phosphor) may beattached to light guide 230 held in place via a suitable supportstructure (not illustrated), disposed within the extractor (also notillustrated) or otherwise arranged, for example. Wavelength-conversionmaterial that is disposed within the extractor may be configured as ashell or other object and disposed within a notional area that iscircumscribed between R/n and R*(1+n²)^((−1/2)), where R is the radiusof curvature of the light-exit surfaces (246 and 248 in FIG. 2A) of theextractor 240 and n is the index of refraction of the portion of theextractor that is opposite of the wavelength-conversion material asviewed from the reflective surfaces (242 and 244 in FIG. 2A). Thesupport structure may be a transparent self-supporting structure. Thewavelength-conversion material diffuses light as it converts thewavelengths, provides mixing of the light and can help uniformlyilluminate a surface of the ambient environment.

During operation, light exiting light guide 230 through end 232 impingeson the reflective interfaces at portions of the redirecting surface 242and 244 and is reflected outwardly towards output surfaces 246 and 248,respectively, away from the symmetry plane of the luminaire module. Thefirst portion of the redirecting surface 242 provides light having anangular distribution 138 towards the output surface 246, the secondportion of the redirecting surface 244 provides light having an angulardistribution 138′ towards the output surface 246. The light exitsoptical extractor through output surfaces 246 and 248. In general, theoutput surfaces 246 and 248 have optical power, to redirect the lightexiting the optical extractor 240 in angular ranges 142 and 142′,respectively. For example, optical extractor 240 may be configured toemit light upwards (i.e., towards the plane intersecting the LEEs andparallel to the x-y plane), downwards (i.e., away from that plane) orboth upwards and downwards. In general, the direction of light exitingthe luminaire module through surfaces 246 and 248 depends on thedivergence of the light exiting light guide 230 and the orientation ofsurfaces 242 and 244.

Surfaces 242 and 244 may be oriented so that little or no light fromlight guide 230 is output by optical extractor 240 in certaindirections. In implementations where the luminaire module 200 isattached to a ceiling of a room (e.g., the forward direction is towardsthe floor) such configurations can help avoid glare and an appearance ofnon-uniform illuminance.

In general, the light intensity distribution provided by luminairemodule 200 reflects the symmetry of the luminaire module's structureabout the y-z plane. For example, referring to FIG. 1B, light output inangular range 142′ corresponds to the first output lobe 145 a of thefar-field light intensity distribution 101, light output in angularrange 142 corresponds to the second output lobe 145 b of the far-fieldlight intensity distribution 101 and light output (leaked) in angularrange 225′ corresponds to the third output lobe 145 c of the far-fieldlight intensity distribution 101. In general, an intensity profile ofluminaire module 200 will depend on the configuration of the opticalcoupler 220, the light guide 230 and the optical extractor 240. Forinstance, the interplay between the shape of the optical coupler 220,the shape of the redirecting surface 243 of the optical extractor 240and the shapes of the output surfaces 246, 248 of the optical extractor240 can be used to control the angular width and prevalent direction(orientation) of the output first 145 a and second 145 b lobes in thefar-field light intensity profile 101. Additionally, a ratio of anamount of light in the combination of first 145 a and second 145 boutput lobes and light in the third output lobe 145 c is controlled byreflectivity and transmissivity of the redirecting surfaces 242 and 244.For example, for a reflectivity of 90% and transmissivity of 10% of theredirecting surfaces 242, 244, 45% of light can be output in the outputangular range 142′ corresponding to the first output lobe 142 a, 45%light can be output in the output angular range 142 corresponding to thesecond output lobe 142 b, and 10% of light can be output in the outputangular range 225′ corresponding to the third output lobe 142 c.

In some implementations, the orientation of the output lobes 145 a, 145b can be adjusted based on the included angle of the v-shaped groove 241formed by the portions of the redirecting surface 242 and 244. Forexample, a first included angle results in a far-field light intensitydistribution 101 with output lobes 145 a, 145 b located at relativelysmaller angles compared to output lobes 145 a, 145 b of the far-fieldlight intensity distribution 101 that results for a second includedangle larger than the first angle. In this manner, light can beextracted from the luminaire module 200 in a more forward direction forthe smaller of two included angles formed by the portions 242, 244 ofthe redirecting surface 243.

Furthermore, while surfaces 242 and 244 are depicted as planar surfaces,other shapes are also possible. For example, these surfaces can becurved or faceted. Curved redirecting surfaces 242 and 244 can be usedto narrow or widen the output lobes 145 a, 145 b. Depending of thedivergence of the angular range 225 of the light that is received at theinput end of the optical extractor 232′, concave reflective surfaces242, 244 can narrow the lobes 145 a, 145 b output by the opticalextractor 240 (and illustrated in FIG. 1B), while convex reflectivesurfaces 242, 244 can widen the lobes 145 a, 145 b output by the opticalextractor 240. As such, suitably configured redirecting surfaces 242,244 may introduce convergence or divergence into the light. Suchsurfaces can have a constant radius of curvature, can be parabolic,hyperbolic, or have some other curvature.

In general, the geometry of the elements can be established using avariety of methods. For example, the geometry can be establishedempirically. Alternatively, or additionally, the geometry can beestablished using optical simulation software, such as Lighttools™,Tracepro™, FRED™ or Zemax™, for example.

In general, luminaire module 200 can be designed to output light intodifferent output angular ranges 142, 142′ from those shown in FIG. 2A.In some implementations, illumination devices can output light intolobes 145 a, 145 b that have a different divergence or propagationdirection than those shown in FIG. 1B. For example, in general, theoutput lobes 145 a, 145 b can have a width of up to about 90° (e.g., 80°or less, 70° or less, 60° or less, 50° or less, 40° or less, 30° orless, 20° or less). In general, the direction in which the output lobes145 a, 145 b are oriented can also differ from the directions shown inFIG. 1B. The “direction” refers to the direction at which a lobe isbrightest. In FIG. 1B, for example, the output lobes 145 a, 145 b areoriented at approx. −130° and approximately +130°. In general, outputlobes 145 a, 145 b can be directed more towards the horizontal (e.g., atan angle in the ranges from −90° to −135°, such as at approx. −90°,approx. −100°, approx. −110°, approx. −120°, approx. −130°, and from+90° to +135°, such as at approx. +90°, approx. +100°, approx. +110°,approx. +120°, approx. +130°.

The luminaire modules can include other features useful for tailoringthe intensity profile. For example, in some implementations, luminairemodules can include an optically diffuse material that can diffuse lightin a controlled manner to aid homogenizing the luminaire module'sintensity profile. For example, surfaces 242 and 244 can be roughened ora diffusely reflecting material, rather than a specular reflectivematerial, can be coated on these surfaces. Accordingly, the opticalinterfaces at surfaces 242 and 244 can diffusely reflect light,scattering light into broader lobes than would be provided by similarstructures utilizing specular reflection at these interfaces. In someimplementations these surfaces can include structure that facilitatesvarious intensity distributions. For example, surfaces 242 and 244 caneach have multiple planar facets at differing orientations. Accordingly,each facet will reflect light into different directions. In someimplementations, surfaces 242 and 244 can have structure thereon (e.g.,structural features that scatter or diffract light).

Surfaces 246 and 248 need not be surfaces having a constant radius ofcurvature. For example, surfaces 246 and 248 can include portions havingdiffering curvature and/or can have structure thereon (e.g., structuralfeatures that scatter or diffract light). In certain implementations, alight scattering material can be disposed on surfaces 246 and 248 ofoptical extractor 240.

In some implementations, optical extractor 240 is structured so that anegligible amount (e.g., less than 1%) of the light propagating withinat least one plane (e.g., the x-z cross-sectional plane) that isreflected by surface 242 or 244 experiences TIR at light-exit surface246 or 248. For certain spherical or cylindrical structures, a so-calledWeierstrass condition can avoid TIR. A Weierstrass condition isillustrated for a circular structure (i.e., a cross section through acylinder or sphere) having a surface of radius R and a concentricnotional circle having a radius R/n, where n is the refractive index ofthe structure. Any light ray that passes through the notional circlewithin the cross-sectional plane is incident on surface of the circularstructure and has an angle of incidence less than the critical angle andwill exit the circular structure without experiencing TIR. Light rayspropagating within the spherical structure in the plane but notemanating from within notional surface can impinge on the surface ofradius R at the critical angle or greater angles of incidence.Accordingly, such light may be subject to TIR and won't exit thecircular structure. Furthermore, rays of p-polarized light that passthrough a notional space circumscribed by an area with a radius ofcurvature that is smaller than R/(1+n²)^((−1/2)), which is smaller thanR/n, will be subject to small Fresnel reflection at the surface ofradius R when exiting the circular structure. This condition may bereferred to as Brewster geometry. Implementations may be configuredaccordingly.

Referring again to FIG. 2A, in some implementations, all or part ofsurfaces 242 and 244 may be located within a notional Weierstrasssurface defined by surfaces 246 and 248. For example, the portions ofsurfaces 242 and 244 that receive light exiting light guide 230 throughend 232 can reside within this surface so that light within the x-zplane reflected from surfaces 242 and 244 exits through surfaces 246 and248, respectively, without experiencing TIR.

In the example implementations described above in connection with FIG.2A, the luminaire module 200 is configured to output light into outputangular ranges 142 and 142′. In other implementations, the lightguide-based luminaire module 200 is modified to output light into asingle output angular range 142′. FIG. 2B shows such light guide-basedluminaire module 200* configured to output light on a single side of thelight guide is referred to as a single-sided luminaire module. Thesingle-sided luminaire module 200* is elongated along the y-axis likethe luminaire module 200 shown in FIG. 2A. Also like the luminairemodule 200, the single-sided luminaire module 200* includes a mount 212and LEEs 210 disposed on a surface of the mount 212 along the y-axis toemit light in a first angular range. The single-sided luminaire module200* further includes optical couplers 220 arranged and configured toredirect the light emitted by the LEEs 210 in the first angular rangeinto a second angular range 225 that has a divergence smaller than thedivergence of the first angular range at least in the x-z cross-section.Also, the single-sided luminaire module 200* includes a light guide 230to guide the light redirected by the optical couplers 220 in the secondangular range 225 from a first end 231 of the light guide to a secondend 232 of the light guide. Additionally, the single-sided luminairemodule 200* includes a single-sided extractor (denoted 240*) to receivethe light guided by the light guide 230. The single-sided extractor 240*includes a redirecting surface 244 to redirect the light received fromthe light guide 230 into a third angular range 138′, like described forluminaire module 200 with reference to FIG. 2A, and an output surface248 to output the light redirected by the redirecting surface 244 in thethird angular range 138′ into a fourth angular range 142′.

A light intensity profile of the single-sided luminaire module 200* isrepresented in FIG. 1B as a single output lobe 145 a. The single outputlobe 145 a corresponds to light output by the single-sided luminairemodule 200* in the fourth angular range 142′.

FIG. 2C shows an embodiment 200′ of the luminaire module 200 that alsois elongated along an axis (e.g., y-axis) perpendicular to the forwarddirection (e.g., along the z-axis.) In this case, a length L of thelight guide 230 along the elongated dimension of the luminaire module200′ can be 2′, 4′ or 8′, for instance. A thickness T of the light guide230 orthogonal to the elongated dimension L (e.g., along the x-axis) ischosen to be a fraction of the distance D traveled by the guided lightfrom the receiving end to the opposing end of the light guide 230. ForT=0.05 D, 0.1 D or 0.2 D, for instance, light from multiple, point-likeLEEs 210—distributed along the elongated dimension L—that isedge-coupled into the light guide 230 at the receiving end canefficiently mix and become uniform (quasi-continuous) along the y-axisby the time it propagates to the opposing end.

FIG. 2D shows a luminaire module 200″ that has (e.g., continuous ordiscrete) rotational symmetry about the forward direction (e.g.,z-axis.) Here, a diameter T of the light guide 230 is a fraction of thedistance D traveled by the guided light from the receiving end to theopposing end of the light guide 230. For example, the diameter of thelight guide 230 can be T=0.05 D, 0.1 D or 0.2 D, for instance.

Other open and closed shapes of the luminaire module 200 are possible.FIGS. 2E and 2F show a perspective view and a bottom view, respectively,of a luminaire module 200″ for which the light guide 230 has twoopposing side surfaces 232 a, 232 b that form a closed cylinder shell ofthickness T. In the example illustrated in FIGS. 2E and 2F, the x-ycross-section of the cylinder shell formed by the opposing side surfaces232 a, 232 b is oval. In other cases, the x-y cross-section of thecylinder shell can be circular or can have other shapes. Someimplementations of the example luminaire module 200″ may include aspecular reflective coating on the side surface 232 a of the light guide230. For T=0.05 D, 0.1 D or 0.2 D, for instance, light from multiple,point-like LEEs 210—distributed along an elliptical path of lengthL—that is edge-coupled into the light guide 230 at the receiving end canefficiently mix and become uniform (quasi-continuous) along such anelliptical path by the time it propagates to the opposing end.

Light guided luminaire modules like the ones described in thissection—for which the light guide provides guided light directly to anoptical extractor without the use of a light divergence modifier—can beused to obtain luminaire modules that include a combination of a lightguide and a light divergence modifier, as described in the followingsections.

(iii) Light Guide Illumination Devices with Different Light DivergenceModifiers

FIGS. 3A-3G show aspects of an illumination device 300-j that includes acombination of a light guide 330 and a light divergence modifier 350-j,where j is in {a, b, c, d, e, f, g}. In these examples, the illuminationdevice 300-j also includes LEEs 310, one or more corresponding opticalcouplers 320 and an optical extractor 340. In some implementations, theillumination device 300-j has an elongated configuration, e.g., as shownin FIG. 2C, with a longitudinal dimension L along the y-axis(perpendicular to the page in FIG. 3A.) In this case, L can be 1′, 2′ or4′, for instance. In other implementations, the illumination device300-j can have another elongated configuration, as illustrated in FIGS.2E-2F. In some other implementations, the illumination device 300-j canhave a non-elongated configuration, e.g., with rotational symmetryaround the z-axis, as illustrated in FIG. 2D.

The LEEs 310 are disposed on a substrate 312 and have a structuresimilar to a structure of the LEEs 110 of the illumination device 100described above in connection with FIG. 1A or a structure of the LEEs210 of the luminaire modules 200, 200*, 200′, 200″, 200′″ describedabove in connection with FIGS. 2A-2E.

Further, the optical couplers 320 have a structure similar to astructure of the optical couplers 120 of the illumination device 100described above in connection with FIG. 1A or a structure of the opticalcouplers 220 of the luminaire modules 200, 200*, 200′, 200″, 200′″described above in connection with FIGS. 2A-2E. Furthermore, the lightguide 330 has a structure similar to a structure of the light guide 130of the illumination device 100 described above in connection with FIG.1A or a structure of the light guide 230 of the luminaire modules 200,200*, 200′, 200″, 200′″ described above in connection with FIGS. 2A-2E.Here, the light guide 330 has a length D along the z-axis, e.g., D=10,20, 50 cm, from a receiving end to an opposing end, and a thickness Talong the x-axis that can be much smaller than the length D, e.g., T 5%D, 10% D or 20% D. The optical couplers 320 are optically coupled to theinput end of the light guide 330. In some implementations, the opticalcouplers 320 are bonded to the input end of the light guide 330. Inother implementations, the optical couplers 320 and the light guide 330are integrally formed.

The light divergence modifier 350-j, for j in {a, b, c, d, e, f}, has aninput aperture and an output aperture separated by a distance Δ, whichrepresents a length of the light divergence modifier 350-j. Here, thelength Δ of the light divergence modifier 350-j is between 0.05 D≤Δ≤0.5D, e.g., 0.1 D, 0.2 D, 0.3 D, or 0.4 D. The input aperture of the lightdivergence modifier 350-j is optically coupled to the output end of thelight guide 330. In some implementations, the input aperture of thelight divergence modifier 350-j is bonded to the output end of the lightguide 330. In other implementations, the light guide 330 and the lightdivergence modifier 350-j are integrally formed. The output aperture ofthe light divergence modifier 350-j is optically coupled to the opticalextractor 340. In some implementations, the output aperture of the lightdivergence modifier 350-j is bonded to the optical extractor 340. Inother implementations, the light divergence modifier 350-j and theoptical extractor 340 are integrally formed. Alternatively, the lightdivergence modifier 350-g of an illumination device 300-g is aninterface between the light guide 330 and the optical extractor 340configured as a two dimensional (2D) grating. In this case, the length Δof the light divergence modifier 150 collapses to zero, Δ→0, and theinput aperture of the light divergence modifier 350-g represents a sideof the interface adjacent to the light guide 330, and the outputaperture of the light divergence modifier 350-g represents a side of theinterface adjacent to the optical extractor 340.

Moreover, the optical extractor 340 has a structure similar to astructure of the optical extractor 130 of the illumination device 100described above in connection 1A or a structure of the optical extractor240/240* of the luminaire modules 200, 200*, 200′, 200″, 200′″ describedabove in connection with FIGS. 2A-2E.

During operation, the LEEs 310 emit light within a first angular range115 relative to the z-axis. The one or more couplers 320 are configuredto receive the light from the LEEs 310 within the first angular range115 and provide light within a second angular range 125 to the lightguide 330. Here, the divergence of the second angular range 125 issmaller than the divergence of the first angular range 115, such thatthe combination (i) of the second angular range 125 and (ii) a numericalaperture of the light guide 330 is chosen to allow for the lightreceived from the one or more couplers 320 at the receiving end of thelight guide 330 to propagate to the opposing end of the light guide 330,for example, via TIR.

In this manner, the light received by the light guide 330 at thereceiving end from the one or more couplers 320 in the second angularrange 125 is guided forward (along the z-axis) by the light guide 330from its receiving end to its opposing end. At the opposing end, theguided light has a third angular range 135. In some implementations, thethird angular range 135 is substantially the same as the second angularrange 125. Guided light provided by the light guide 330 at the opposingend in an angular range 135 is received at the input aperture of thelight divergence modifier 350-j. The guided light received at the inputaperture is modified by the light divergence modifier 350-j such thatmodified light provided at the output aperture of the light divergencemodifier 350-j has a modified angular range 155 different from theguided angular range 135. The modified light provided by the lightdivergence modifier 350-j at the output aperture in an angular range 155is received by the optical extractor 340. The modified light received bythe optical extractor 340 is output by the optical extractor 340 infirst and second backward output angular ranges 145′ and 145″, andoptionally in third forward output angular range 145″. In this example,a direction of propagation of the output light in the first backwardoutput angular range 145′ has a component in the backward direction(antiparallel with the z-axis) and another component to the right of thelight guide 330 (parallel with the x-axis). Further, a direction ofpropagation of the output light in the second backward output angularrange 145″ has a component in the backward direction (antiparallel withthe z-axis) and another component to the left of the light guide 130(antiparallel with the x-axis). Optionally, a direction of propagationof the output light in the third forward output angular range 145′″ isalong the forward direction (parallel with the z-axis).

Various embodiments of the light divergence modifier 350-j, where j isin {a, b, c, d, e, f, g}, are described below.

Example 1: Tapered Light Divergence Modifier

FIG. 3A shows an illumination device 300-a that includes a combinationof the light guide 330 and a tapered light divergence modifier 350-a.The tapered light divergence modifier 350-a has an input aperture and anoutput aperture, such the input aperture is wider than the outputaperture. Further, the input and output apertures are separated by adistance Δ, which represents a length of the tapered light divergencemodifier 350-a. Here, the length Δ of the tapered light divergencemodifier 350-a is between 0.05 D≤Δ≤0.5 D, e.g., 0.1 D, 0.2 D, 0.3 D, or0.4 D, where D is the distance between the input end and the output endof the light guide 330. The input aperture of the tapered lightdivergence modifier 350-a is optically coupled to the output end of thelight guide 330. In some implementations, the input aperture of thetapered light divergence modifier 350-a is bonded to the output end ofthe light guide 330. In other implementations, the light guide 330 andthe tapered light divergence modifier 350-a are integrally formed. Theoutput aperture of the tapered light divergence modifier 350-a isoptically coupled to the optical extractor 340. In some implementations,the output aperture of the tapered light divergence modifier 350-a isbonded to the optical extractor 340. In other implementations, thetapered light divergence modifier 350-a and the optical extractor 340are integrally formed.

Further, the tapered light divergence modifier 350-a can be made from amaterial having the same refractive index n_(350a) as a refractive indexn₃₃₀ of a material from which the light guide 330 is made,n_(350a)≈n₃₃₀, and/or as a refractive index n₃₄₀ of a material fromwhich the optical extractor 340 is made, n_(350a)≈n₃₄₀. In some suchcases, n₃₃₀≈n₃₄₀. Alternatively, the tapered light divergence modifier350-a can be made from a material having a different refractive indexn_(350a) relative to a refractive index n₃₃₀ of a material from whichthe light guide 330 is made, n_(350a)≠n₃₃₀, and/or relative to arefractive index n₃₄₀ of a material from which the optical extractor 340is made, n_(350a)≠n₃₄₀. When the light guide 330, the tapered lightdivergence modifier 350-a, and/or the optical extractor 340 are madefrom solid materials, their respective refractive indices n₃₃₀, n_(350a)and/or n₃₄₀ are larger than 1. When the light guide 330, the taperedlight divergence modifier 350-a, and/or the optical extractor 340 arehollow, their respective refractive indices n₃₃₀, n_(350a) and/or n₃₄₀are equal to 1.

As the input aperture of the tapered light divergence modifier 350-a islarger than its output aperture, divergence of the modified angularrange 155 of the modified light provided by the tapered light divergencemodifier 350-a at the output interface is larger than divergence of theguided angular range 135 of the guided light received by the taperedlight divergence modifier 350-a at the input aperture. A set ofparameters determines a ratio of the divergence of the modified angularrange 155 of the modified light provided by the tapered light divergencemodifier 350-a at the output interface to the divergence of the guidedangular range 135 of the guided light received by the tapered lightdivergence modifier 350-a at the input aperture. This set of parametersincludes (i) a ratio of a cross-section sin (e.g., in the x-y plane) ofthe input aperture to a cross-section S_(out) (e.g., in the x-y plane)of the output aperture; (ii) the length Δ of the tapered lightdivergence modifier 350-a; (iii) a relative refractive indexn₃₃₀/n_(350a) of a material from which the light guide 330 is made and amaterial from which the tapered light divergence modifier 350-a is made;and (iv) a relative refractive index n_(350a)/n₃₄₀ of a material fromwhich the tapered light divergence modifier 350-a is made and a materialfrom which the optical extractor 340 is made.

When the illumination device 300-a is elongated along the y-axis(perpendicular to the page), the tapered light divergence modifier 350-aincludes a pair of opposing side surfaces (e.g., orthogonal to the x-zplane) extending along the length Δ of the tapered light divergencemodifier 350-a (along the z-axis) between the input aperture and theoutput aperture. For example, the light received at the input aperturepropagates to the output aperture by specularly reflecting between thepair of opposing side surfaces. As another example, when the taperedlight divergence modifier 350-a is made from a solid material, the lightreceived at the input aperture propagates to the output aperture via TIRreflections between the pair of opposing side surfaces. In the latterexample, the parameters (i), (ii), (iii) and (iv) are selected such thatthe light propagating through the tapered light divergence modifier350-a is incident on each of the pair of opposing side surfaces atangles larger than a critical angle, over the entire length Δ of thetapered light divergence modifier 350-a.

Moreover, in some cases, at least one of the opposing side surfaces isplanar. In some cases, both of the opposing side surfaces are planar.Here, the tapered light divergence modifier 350-a can be shaped as atruncated prism with rectangular bases (where the bases are parallel tothe x-y plane, for instance.) When the illumination device 300-a hasrotational symmetry around the z-axis, the tapered light divergencemodifier 350-a can be shaped as a truncated prism with rotationallysymmetric bases (where the bases are parallel to the x-y plane, forinstance.) Examples of rotationally symmetric bases are circles,equilateral triangles, squares, hexagons, octagons, etc.

Example 2: Flared Light Divergence Modifier

FIG. 3B shows a portion of an illumination device 300-b that includes acombination of the light guide 330 and a flared light divergencemodifier 350-b. The flared light divergence modifier 350-b has an inputaperture and an output aperture, such the input aperture is narrowerthan the output aperture. Further, the input and output apertures areseparated by a distance Δ, which represents a length of the flared lightdivergence modifier 350-b. Here, the length Δ of the flared lightdivergence modifier 350-b is between 0.05 D≤Δ≤0.5 D, e.g., 0.1 D, 0.2 D,0.3 D, or 0.4 D, where D is the distance between the input end and theoutput end of the light guide 330. The input aperture of the flaredlight divergence modifier 350-b is optically coupled to the output endof the light guide 330. In some implementations, the input aperture ofthe flared light divergence modifier 350-b is bonded to the output endof the light guide 330. In other implementations, the light guide 330and the flared light divergence modifier 350-b are integrally formed.The output aperture of the flared light divergence modifier 350-b isoptically coupled to the optical extractor 340. In some implementations,the output aperture of the flared light divergence modifier 350-b isbonded to the optical extractor 340. In other implementations, theflared light divergence modifier 350-b and the optical extractor 340 areintegrally formed.

Further, the flared light divergence modifier 350-b can be made from amaterial having the same refractive index n_(350b) as a refractive indexn₃₃₀ of a material from which the light guide 330 is made,n_(350b)≈n₃₃₀, and/or as a refractive index n₃₄₀ of a material fromwhich the optical extractor 340 is made, n_(350b)≈n₃₄₀. In some suchcases, n₃₃₀≈n₃₄₀. Alternatively, the flared light divergence modifier350-b can be made from a material having a different refractive indexn_(350b) relative to a refractive index n₃₃₀ of a material from whichthe light guide 330 is made, n_(350b)≠n₃₃₀, and/or relative to arefractive index n₃₄₀ of a material from which the optical extractor 340is made, n_(350b)≠n₃₄₀. When the light guide 330, the flared lightdivergence modifier 350-b, and/or the optical extractor 340 are madefrom a solid material, their respective refractive indices n₃₃₀,n_(350b) and/or n₃₄₀ are larger than 1. When the light guide 330, theflared light divergence modifier 350-b, and/or the optical extractor 340are hollow, their respective refractive indices n₃₃₀, n_(350b) and/orn₃₄₀ are equal to 1.

As the input aperture of the flared light divergence modifier 350-b islarger than its output aperture, divergence of the modified angularrange 155 of the modified light provided by the flared light divergencemodifier 350-b at the output interface is smaller than divergence of theguided angular range 135 of the guided light received by the flaredlight divergence modifier 350-b at the input aperture. A set ofparameters determines a ratio of the divergence of the modified angularrange 155 of the modified light provided by the flared light divergencemodifier 350-b at the output interface to the divergence of the guidedangular range 135 of the guided light received by the flared lightdivergence modifier 350-b at the input aperture. This set of parametersincludes (i) a ratio of a cross-section sin (e.g., in the x-y plane) ofthe input aperture to a cross-section S_(out) (e.g., in the x-y plane)of the output aperture; (ii) the length Δ of the flared light divergencemodifier 350-b; (iii) a relative refractive index n₃₃₀/n_(350b) of amaterial from which the light guide 330 is made and a material fromwhich the flared light divergence modifier 350-b is made; and (iv) arelative refractive index n_(350b)/n₃₄₀ of a material from which theflared light divergence modifier 350-b is made and a material from whichthe optical extractor 340 is made.

When the illumination device 300-b is elongated along the y-axis(perpendicular to the page), the flared light divergence modifier 350-bincludes a pair of opposing side surfaces (e.g., orthogonal to the x-zplane) extending along the length Δ of the flared light divergencemodifier 350-b (along the z-axis) between the input aperture and theoutput aperture. For example, the light received at the input aperturepropagates to the output aperture by specularly reflecting between thepair of opposing side surfaces. As another example, when the flaredlight divergence modifier 350-b is made from a solid material, the lightreceived at the input aperture propagates to the output aperture via TIRreflections between the pair of opposing side surfaces.

Moreover, in some cases, at least one of the opposing side surfaces isplanar. In some cases, both of the opposing side surfaces are planar.Here, the flared light divergence modifier 350-b can be shaped as atruncated prism with rectangular bases (where the bases are parallel tothe x-y plane, for instance.) When the illumination device 300-b hasrotational symmetry around the z-axis, the flared light divergencemodifier 350-b can be shaped as a truncated prism with rotationallysymmetric bases (where the bases are parallel to the x-y plane, forinstance.) Examples of rotationally symmetric bases are circles,equilateral triangles, squares, hexagons, octagons, etc.

Example 3: Lensed Light Divergence Modifier

FIGS. 3C, 3D and 3E show respective portions of illumination devices300-j that includes a combination of the light guide 330 and a lensedlight divergence modifier 350-j, where j is in {c, d, e}. The lensedlight divergence modifier 350-j is a lens (or a lens assembly including2, 3 or more optically coupled lenses) that has an input face and anoutput face separated by a distance Δ, which represents a thickness ofthe lensed light divergence modifier 350-j. Here, the length Δ of thelensed light divergence modifier 350-j is between 0.02 D≤Δ≤0.1 D, e.g.,0.04 D, 0.06 D or 0.08 D where D is the distance between the input endand the output end of the light guide 330. Moreover, the input face ofthe lensed light divergence modifier 350-j is bonded to the output endof the light guide 330, and the output face of the lensed lightdivergence modifier 350-j is bonded to the optical extractor 340. Here,the lensed light divergence modifier 350-j is made from a materialhaving a refractive index n_(350j) that is different relative to arefractive index n₃₃₀ of a material from which the light guide 330 ismade, n_(350j)≠n₃₃₀, and/or relative to a refractive index n₃₄₀ of amaterial from which the optical extractor 340 is made, n_(350j)≠n₃₄₀,where j is in {c, d, e}.

A set of parameters determines a ratio of the divergence of the modifiedangular range 155 of the modified light provided by the lensed lightdivergence modifier 350-j through the output face to the divergence ofthe guided angular range 135 of the guided light received by the lensedlight divergence modifier 350-j through the input face. This set ofparameters includes (i) an effective focal length, fj, where j is in {c,d, e}, of the lens (or the lens assembly) that forms the lensed lightdivergence modifier 350-j; (ii) the thickness Δ of the lens (or the lensassembly) that forms the lensed light divergence modifier 350-j; (iii) arelative refractive index n₃₃₀/n_(350j) of a material from which thelight guide 330 is made and a material from which the lensed lightdivergence modifier 350-j is made; and (iv) a relative refractive indexn_(350j)/n₃₄₀ of a material from which the lensed light divergencemodifier 350-j is made and a material from which the optical extractor340 is made.

In the example illustrated in FIG. 3C, the lensed light divergencemodifier 350-c of the illumination device 300-c includes a convergentlens with a positive focal length f_(c). As such, divergence of themodified angular range 155 of the modified light provided by the lensedlight divergence modifier 350-c through the output face is smaller thandivergence of the guided angular range 135 of the guided light receivedby the lensed light divergence modifier 350-c through the input face.When the relative refractive indices n_(350c)/n₃₃₀ and n_(350c)/n₃₄₀ arelarger than 1, in some implementations, the input face of the convergentlens is convex and the output face of the convergent lens is flat orconcave relative to the propagation direction of light through thelensed light divergence modifier 350-c (e.g., along the z-axis.) In someimplementations, the input face of the convergent lens is convex or flatand the output face of the convergent lens is concave relative to thepropagation direction of light through the lensed light divergencemodifier 350-c (e.g., along the z-axis.) However, when the relativerefractive indices n_(350c)/n₃₃₀ and n_(350c)/n₃₄₀ are less than 1, insome implementations, the input face of the convergent lens is concaveand the output face of the convergent lens is flat or convex relative tothe propagation direction of light through the lensed light divergencemodifier 350-c (e.g., along the z-axis.) In some implementations, theinput face of the convergent lens is concave or flat and the output faceof the convergent lens is convex relative to the propagation directionof light through the lensed light divergence modifier 350-c (e.g., alongthe z-axis.)

In the example illustrated in FIG. 3D, the lensed light divergencemodifier 350-d of the illumination device 300-d includes a divergentlens with a negative focal length f_(d). As such, divergence of themodified angular range 155 of the modified light provided by the lensedlight divergence modifier 350-d through the output face is larger thandivergence of the guided angular range 135 of the guided light receivedby the lensed light divergence modifier 350-d through the input face.When the relative refractive indices n_(350d)/n₃₃₀ and n_(350d)/n₃₄₀ arelarger than 1, in some implementations, the input face of the divergentlens is concave and the output face of the divergent lens is flat orconvex relative to the propagation direction of light through the lensedlight divergence modifier 350-d (e.g., along the z-axis.) In someimplementations, the input face of the divergent lens is concave or flatand the output face of the divergent lens is concave relative to thepropagation direction of light through the lensed light divergencemodifier 350-d (e.g., along the z-axis.) However, when the relativerefractive indices n_(350d)/n₃₃₀ and n_(350d)/n₃₄₀ are less than 1, insome implementations, the input face of the divergent lens is convex andthe output face of the divergent lens is flat or concave relative to thepropagation direction of light through the lensed light divergencemodifier 350-d (e.g., along the z-axis.) In some implementations, theinput face of the divergent lens is convex or flat and the output faceof the divergent lens is concave relative to the propagation directionof light through the lensed light divergence modifier 350-d (e.g., alongthe z-axis.)

In the example illustrated in FIG. 3E, the lensed light divergencemodifier 350-e of the illumination device 300-e includes a Fresnel lenswith a desired positive or negative focal length f_(e). At least one ofthe input or output faces of the Fresnel lens is faceted. In thismanner, the thickness of the lensed light divergence modifier 350-e canbe smaller than the thickness of the convergent lens of the lensed lightdivergence modifier 350-c or the divergent lens of the lensed lightdivergence modifier 350-d. In order for divergence of the modifiedangular range 155 of the modified light provided by the lensed lightdivergence modifier 350-e through the output face to be smaller thandivergence of the guided angular range 135 of the guided light receivedby the lensed light divergence modifier 350-e through the input face,shapes and arrangement of the facets of the input and output faces ofthe lensed light divergence modifier 350-e and relative refractiveindices n_(350e)/n₃₃₀ and n_(350e)/n₃₄₀ are selected to cause a positiveeffective focal length of the Fresnel lens. Alternatively, fordivergence of the modified angular range 155 of the modified lightprovided by the lensed light divergence modifier 350-e through theoutput face to be larger than divergence of the guided angular range 135of the guided light received by the lensed light divergence modifier350-e through the input face, shapes and arrangement of the facets ofthe input and output faces of the lensed light divergence modifier 350-eand relative refractive indices n_(350e)/n₃₃₀ and n_(350e)/n₃₄₀ areselected to cause a negative effective focal length of the Fresnel lens.

Example 4: Diffractive Light Divergence Modifier

FIGS. 3F and 3G show respective portions of illumination devices 300-jthat includes a combination of the light guide 330 and a diffractivelight divergence modifier 350-j, where j is in {f, g}.

In the example illustrated in FIG. 3F, the diffractive light divergencemodifier 350-f is a 3D grating that has an input face and an output faceseparated by a distance Δ, which represents a thickness of thediffractive light divergence modifier 350-f. Here, the thickness Δ ofthe diffractive light divergence modifier 350-j is between 0.02 D≤Δ≤0.1D, e.g., 0.04 D, 0.06 D or 0.08 D, where D is the distance between theinput end and the output end of the light guide 330. This example ofdiffractive light divergence modifier is referred to as a 3D diffractivelight divergence modifier 350-f. In some implementations, the input faceof the 3D diffractive light divergence modifier 350-f is bonded to theoutput end of the light guide 330, and the output face of the 3Ddiffractive light divergence modifier 350-f is bonded to the opticalextractor 340. In some implementations, the 3D diffractive lightdivergence modifier 350-f is integrally formed with the light guide 330,the optical extractor 340, or both.

The 3D grating (also referred to as a volume grating) includes portionsof a volume of the 3D diffractive light divergence modifier 350-f with arefractive index different from a refractive index of a material fromwhich the bulk of the 3D diffractive light divergence modifier 350-f isformed, such that these portions are arranged in a 3D pattern. Forexample, the 3D pattern can be a 3D lattice. As another example, the 3Dpattern can be ordered in at least one direction, and disordered (e.g.,randomly or pseudo-randomly) in the remaining direction(s). In somecases, the foregoing portions of the 3D diffractive light divergencemodifier 350-f that form the 3D pattern can be voids in the bulk of thediffractive light divergence modifier 350-f. In other cases, theforegoing portions of the 3D diffractive light divergence modifier 350-fthat form the 3D pattern can be inserts (metal flakes, dielectricspheres, etc.) in the bulk of the 3D diffractive light divergencemodifier 350-f, such that a refractive index of the inserts is differentfrom the refractive index of the bulk material.

In some implementations, such a 3D grating can be a photonic crystal. Inother implementations, the 3D grating can be a volumetric hologram. The3D patterns of the foregoing 3D gratings can be generated usingmicromachining, laser writing/printing, ion-implantation, etc.

Moreover, the 3D grating can be configured such that the divergence ofthe modified angular range 155 of the modified light provided by the 3Ddiffractive light divergence modifier 350-f through the output face andthe divergence of the guided angular range 135 of the guided lightreceived by the 3D diffractive light divergence modifier 350-f throughthe input face obey a target ratio. In some cases, the target ratio islarger than 1, such that the modified light provided by the 3Ddiffractive light divergence modifier 350-f spreads relative to theguided light provided by the light guide 330. In other cases, the targetratio is smaller than 1, such that the modified light provided by the 3Ddiffractive light divergence modifier 350-f focuses relative to theguided light provided by the light guide 330.

When the illumination device 300-f is elongated along the y-axis(perpendicular to the page), the 3D diffractive light divergencemodifier 350-f includes a pair of opposing side surfaces (e.g.,orthogonal to the x-z plane) extending along the thickness Δ of the 3Ddiffractive light divergence modifier 350-f (along the z-axis) betweenthe input face and the output face. The light received at the input facepropagates to the output face by diffracting off the 3D pattern of the3D grating included in the 3D diffractive light divergence modifier350-f Here, the 3D diffractive light divergence modifier 350-f can beshaped as a prism with rectangular bases (where the bases are parallelto the x-y plane, for instance.) When the illumination device 300-f hasrotational symmetry around the z-axis, the 3D diffractive lightdivergence modifier 350-f can be shaped as a prism with rotationallysymmetric bases (where the bases are parallel to the x-y plane, forinstance.) Examples of rotationally symmetric bases are circles,equilateral triangles, squares, hexagons, octagons, etc.

In the example illustrated in FIG. 3G, the diffractive light divergencemodifier 350-g is an optical interface between the output end of thelight guide 330 and the optical extractor 340. Here, the opticalinterface is configured as a 2D grating that has an input side and anoutput side. The input side is adjacent to the output end of the lightguide 330 and the output side is adjacent to the optical extractor 340.This example of diffractive light divergence modifier is referred to asa 2D diffractive light divergence modifier 350-g.

The 2D grating (also referred to as a surface grating) includes portionsof the optical interface between the light guide 330 and the opticalextractor 340 with a refractive index different from a refractive indexn₃₃₀ of a material from which the light guide 330 is formed and/or arefractive index n₃₄₀ of a material from which the optical extractor 340is formed, such that these portions are arranged in a 2D pattern. Forexample, the 2D pattern can be a 2D lattice. As another example, the 2Dpattern can be ordered only in one direction, and disordered (e.g.,randomly or pseudo-randomly) in a remaining, orthogonal direction. Insome cases, the foregoing portions of the 2D diffractive lightdivergence modifier 350-g that form the 2D pattern can be voids locatedat the interface between the light guide 330 and the optical extractor340. In other cases, the foregoing portions of the 2D diffractive lightdivergence modifier 350-g that form the 2D pattern can be inserts (metalflakes, dielectric spheres, etc.) located at the interface between thelight guide 330 and the optical extractor 340, such that a refractiveindex of the inserts is different from the refractive index n₃₃₀ of thematerial from which the light guide 330 is formed and/or the refractiveindex n₃₄₀ of the material from which the optical extractor 340 isformed. In some other cases, the foregoing portions of the 2Ddiffractive light divergence modifier 350-g that form the 2D pattern canbe grooves, indentations or bumps formed at the interface between thelight guide 330 and the optical extractor 340. In yet some other cases,the 2D pattern can be a surface hologram formed at the interface betweenthe light guide 330 and the optical extractor 340.

In either of the foregoing cases, a thickness Δ of the 2D diffractivelight divergence modifier 350-f is very thin in comparison to thedistance D between the input end and the output end of the light guide330, Δ<<D or Δ→0. For instance the out-of-plane thickness Δ of the 2Dgrating can be of order 0.01 mm, of order 0.1 mm or of order 1 mm.

Moreover, the 2D grating can be configured such that the divergence ofthe modified angular range 155 of the modified light provided by the 2Ddiffractive light divergence modifier 350-g through the output side andthe divergence of the guided angular range 135 of the guided lightreceived by the 2D diffractive light divergence modifier 350-g throughthe input face obey a target ratio. In some cases, the target ratio islarger than 1, such that the modified light provided by the 2Ddiffractive light divergence modifier 350-g spreads relative to theguided light provided by the light guide 330. In other cases, the targetratio is smaller than 1, such that the modified light provided by the 2Ddiffractive light divergence modifier 350-g focuses relative to theguided light provided by the light guide 330.

When the illumination device 300-g is elongated along the y-axis(perpendicular to the page), the 2D diffractive light divergencemodifier 350-g can be shaped as a rectangular band (where input andoutput sides of the band are parallel to the x-y plane, for instance.)When the illumination device 300-g has rotational symmetry around thez-axis, the 2D diffractive light divergence modifier 350-d can be shapedas a patch with rotationally symmetric input and output sides (that areparallel to the x-y plane, for instance.) Examples of rotationallysymmetric bases are circles, equilateral triangles, squares, hexagons,octagons, etc.

The preceding figures and accompanying description illustrate examplemethods, systems and devices for illumination. It will be understoodthat these methods, systems, and devices are for illustration purposesonly and that the described or similar techniques may be performed atany appropriate time, including concurrently, individually, or incombination. In addition, many of the steps in these processes may takeplace simultaneously, concurrently, and/or in different orders than asshown. Moreover, the described methods/devices may use additionalsteps/parts, fewer steps/parts, and/or different steps/parts, as long asthe methods/devices remain appropriate.

In other words, although this disclosure has been described in terms ofcertain aspects or implementations and generally associated methods,alterations and permutations of these aspects or implementations will beapparent to those skilled in the art. Accordingly, the above descriptionof example implementations does not define or constrain this disclosure.Further implementations are described in the following claims.

What is claimed is:
 1. An illumination device comprising: a plurality oflight-emitting elements (LEEs) to emit light having a first divergence;one or more optical couplers to redirect emitted light, each opticalcoupler having a receiving aperture optically coupled with acorresponding one or more LEEs to receive the emitted light, and furtherhaving an opposing aperture, the optical coupler being flared such thatthe receiving aperture is smaller than the opposing aperture, therebylight provided by the optical coupler at the opposing aperture has asecond divergence smaller than the first divergence; a light guidecomprising a pair of opposing side surfaces that are parallel to eachother and extend in a forward direction from a first end of the lightguide to a second end of the light guide, the light guide beingpositioned to receive at the first end light provided by the one or moreoptical couplers and configured to guide the light to the second end,wherein guided light that reaches the second end has a third divergencethat is substantially the same as the second divergence, wherein anumerical aperture of the light guide is such that the light receivedfrom the one or more optical couplers with the second divergence can beguided by the light guide through TIR off the pair of opposing sidesurfaces; a light divergence modifier having an input aperture opticallycoupled to the light guide at the second end to receive the guided lightand further having an output aperture, the light divergence modifierbeing flared such that the input aperture is smaller than the outputaperture, thereby light provided by the light divergence modifier at theoutput aperture has a modified divergence smaller than the thirddivergence of the guided light; and an optical extractor opticallycoupled to the output aperture of the light divergence modifier andcomprising a first redirecting surface, the first redirecting surface ofthe optical extractor being adapted to reflect at least a portion of thelight provided by the light divergence modifier in a first directionthat has a component orthogonal to the forward direction and anothercomponent in a backward direction, such that the optical extractoroutputs into the ambient environment light reflected by the firstredirecting surface as first output light in a first output angularrange, wherein the first output angular range relates to the firstdirection.
 2. The illumination device of claim 1, wherein the lightdivergence modifier comprises a pair of opposing side surfaces extendingalong a length of the light divergence modifier between the inputaperture and the output aperture.
 3. The illumination device of claim 2,wherein at least one of the opposing side surfaces is planar.
 4. Theillumination device of claim 3, wherein both of the opposing sidesurfaces are planar.
 5. The illumination device of claim 2, wherein thelength of the light divergence modifier is a fraction of a length of thelight guide.
 6. The illumination device of claim 5, wherein the fractionis between 5% and 50%.
 7. The illumination device of claim 2, whereinthe light guide, the light divergence modifier and the optical extractorare integrally formed or bonded together.
 8. The illumination device ofclaim 1, wherein the light divergence modifier comprises a truncatedconical shaped surface extending between the input aperture and theoutput aperture.
 9. The illumination device of claim 1, wherein thelight divergence modifier is configured to guide the light received atthe input aperture in the forward direction through total internalreflection (TIR) at the opposing side surfaces.
 10. The illuminationdevice of claim 1, wherein the LEEs are LEDs that emit white light. 11.The illumination device of claim 1, wherein the optical extractorcomprises a second redirecting surface adapted to reflect at least aportion of the light provided by the light divergence modifier in asecond direction that has a component antiparallel to the orthogonalcomponent of the first direction and another component in the backwarddirection, such that the optical extractor outputs into the ambientenvironment light reflected by the second redirecting surface as secondoutput light in a second output angular range, wherein the second outputangular range relates to the second direction.
 12. The illuminationdevice of claim 11, wherein the first redirecting surface and/or thesecond redirecting surface transmits a remaining portion of the lightprovided by the light divergence modifier so that the transmittedportion of the light exits the optical extractor to the ambientenvironment in the forward direction.
 13. The illumination device ofclaim 11, wherein the optical extractor comprises a first curved outputsurface and a second curved output surface positioned in respectivepaths of the light reflected from the first redirecting surface and thesecond redirecting surface, and the first curved output surface and thesecond curved output surface are configured to transmit light incidentthereon to the ambient environment in respective backward angularranges.
 14. The illumination device of claim 1 extends orthogonally tothe forward direction.
 15. The illumination device of claim 14, whereinthe LEEs are arranged orthogonally to the forward direction.